No obvious cause can be isolated to explain the occurrence of the adverse reactions experienced by people changing from
Ritalin SR to Rubifen SR. It is not unexpected that adverse effects are reported after a brand change. This can occur
even when the brand does not actually change, for example in one study, nearly half the participants reported subjective
differences between their own and study-supplied Ventolin inhalers.4 Another study assessing acceptance of
generic drugs (satisfaction, adverse effects), found significant differences between pharmacological classes of drugs,
with less acceptance associated with substitution of drugs acting on the central nervous system.5
The brand change from Ritalin SR to Rubifen SR involved the slow release form of methylphenidate 20 mg. This is said
to be equivalent to two doses of normal release methylphenidate 10 mg, given four to six hours apart. However there is
a lack of evidence of comparisons between the normal and slow release forms. It is claimed that with the slow release
form, the release of methylphenidate is slower and the maximum blood level is lower for a more consistent effect. It is
theoretically possible that Ritalin SR and Rubifen SR could have different release profiles in some people however, when
compared, they were considered to be bioequivalent forms of the same chemical.
Reports of adverse effects in the literature
A literature search using Medline revealed no reports of adverse effects specifically attributable to Rubifen or methylphenidate
brand change. It is known that methylphenidate use in children can be associated with symptoms such as those reported,
however this is very rare.2 The only other country in which the Rubifen brand is marketed is Argentina.
Side effects that can commonly occur when treatment with methylphenidate is first commenced include; nervousness, insomnia,
headache, decreased appetite, abdominal pain, nausea, vomiting and minor cardiovascular effects.6
An overdose of methylphenidate results in overstimulation of the central and sympathetic nervous system and symptoms
may include; vomiting, agitation, tremor, hyperreflexia, muscle twitching, convulsions, euphoria, confusion, hallucinations,
delirium, sweating, tachycardia and hypertension.6
Is it safe to use Rubifen?
Medsafe has stated that it is satisfied that the two brands of methylphenidate SR are bioequivalent and that no safety
issues have been identified at this point.2 However it is investigating the Rubifen brand and conducting independent
testing. AFT Pharmaceuticals, the manufacturer of Rubifen SR, has been asked to urgently provide further data about the
quality and safety of their product.